Ambient Occlusion reduces light accumulation where shapes meet. Think of a plate sitting on a table - the plate shadows the table in greater amounts the closer you get to the where the plate touches because more and more light is blocked.

Ambient Occlusion fakes that effect without doing the actual math involved in raytracing the the light. So it's not as accurate as "real" indirect lighting but is a great alternative sometimes. Using AO has been a trick of animation houses for some time since it is significantly faster to render over multiple frames than actual global types of illumination.

Carrara's implementation of AO is really nice since it doesn't require rendering multiple files with G-buffers and then compositing them afterwards - everything is already completed in the final rendered image.

Mark

Message edited on: 02/09/2006 12:23